06 Jan 2016: Report

Unnatural Balance: How Food Waste Impacts World’s Wildlife

New research indicates that the food discarded in landfills and at sea is having a profound effect on wildlife populations and fisheries. But removing that food waste creates its own ecological challenges.

by richard conniff

The world wastes more than $750 billion worth of food every year — 1.6 billion tons of food left in farm fields, sent to landfills, or otherwise scattered across the countryside, plus another seven million tons of fishery discards at sea. That waste has gotten a lot of attention lately, mostly in terms of human hunger.

Hardly anyone talks about what all that food waste is doing to wildlife. But a growing body of evidence suggests that our casual attitude about waste

Wikimedia Commons

Discarded food can lead to overpopulation of seagulls and other animals, which can affect other wildlife populations.

may be reshaping the way the natural world functions across much of the planet, inadvertently subsidizing some opportunistic predators and thus contributing to the decline of other species, including some that are threatened or endangered.

A new study in the journal Biological Conservation looks, for instance, at California’s Monterey Bay, where the threatened steelhead trout population has declined by 80 to 90 percent over the past century. Efforts to restore the species along the Pacific Coast have focused on major initiatives like the recent demolition of a dam that had blocked access to critical steelhead breeding grounds on the Carmel River, which empties into Monterey Bay.

But a team of co-authors led by Ann-Marie Osterback, a marine ecologist at the University of California-Santa Cruz, suspects that garbage and fishery discards might also play an underrated part in the problem. The hypothesis is that local food wastes inadvertently subsidize Western gulls in the Monterrey Bay area, and these gulls in turn prey on the juvenile steelhead trout.

The dramatic decline in steelhead numbers would normally mean that fish-eating birds around Monterey Bay would have to move down the food chain to survive. That’s what’s happened to Brandt’s cormorants and marbled murrelets, and their populations have declined as a result.

Animals have been picking up the food scraps forever, but nothing in history approaches the scale of modern food waste.

But according to Osterback, the number of gulls have doubled or quadrupled in different parts of the bay just since the 1980s — thanks to a steady diet of landfill garbage and fishery discards. Osterback and her co-authors found that each individual gull now eats less steelhead than in the past, but the combination of a greatly increased gull population and a severely reduced run of steelhead trout adds up to a dramatic rise in predation pressure. She estimates that the gulls may eat up to 30 percent of juvenile steelhead en route to the sea.

Likewise, yellow-legged gulls subsidized by food wastes in the western Mediterranean, threaten Auduoin’s gulls, European storm petrels, and other vulnerable seabirds through increased predation pressure. Off the coast of Alaska, fishery-subsidized killer whales imperil near-threatened Steller sea lions. And on the western side of the Mojave Desert, common ravens and coyotes that feed on garbage from nearby communities are jeopardizing the recovery of the threatened desert tortoise.

“Ravens scavenge when refuse or carrion are available but they are also capable hunters,” a study in Ecology found. The researchers put out 100 dummy models of juvenile desert tortoises and found that ravens attacked 29 of them over a two-month period. Other studies have linked subsidized ravens to the decline of such threatened or endangered species as marbled murrelets, California least terns, snowy plovers, San Clemente loggerhead shrikes, and sandhill cranes.

Animals have of course been picking up the food scraps we leave behind forever — or at least long enough to change the course of their evolution. That’s how certain wolves evolved into domestic dogs. But nothing in the history of the planet approaches the scale of modern food waste, in farm fields, on streets and beaches, in landfills, and strewn behind fishing boats.

Controlling garbage is not new as a conservation tool, but it has sparked one of the nastiest fights in U.S. conservation.

This abundance of garbage is also a factor in the resurgence of brown bears (population 17,000) and wolves (population 11,000) in modern Europe. Garbage is also the main reason leopards have been able to adapt to living in and around major cities in India. They prey on other animals that scavenge from abundant garbage — dogs, pigs, goats, and rats — and they also feed directly on butchered carcasses discarded in the open.

Removing or controlling garbage is not new as a conservation tool. The U.S. National Park Service did it in the 1970s at Yellowstone National Park, closing dumps and ending the artificial feeding of bears there. But it also sparked one of the nastiest fights in the history of U.S. conservation, especially as the park service began killing or translocating “incorrigible” bears. Cut off from their familiar food sources, the grizzlies struggled and their population declined for a time. Gradually, though, the bears shifted to a more natural diet, moved away from the roads, and ultimately flourished. The Yellowstone grizzly population has roughly quadrupled since the end of artificial feeding in the 1970s, to about 700 bears in 2014.

Measures to address the garbage problem on a broader scale today will likely be at least as challenging. On the one hand, such measures can reduce populations of subsidized predators without the controversy caused by programs to kill or relocate nuisance animals. A study in France demonstrated that closing a dump led to a 49-percent decline in fertility of herring gulls, which are also opportunistic predators. Another study in the western Mediterranean found that a temporary moratorium on trawling had a dramatic impact on gull reproduction, by removing the discards that can otherwise make up as much as 73 percent of their diet.

But when the European Union was debating a ban on fishery discards in 2013, ecologists warned of “unforeseen knock-on consequences.” They pointed out that 52 percent of seabird species worldwide now scavenge fishery discards to some degree. A ban would leave some species hungry,

In an e360 video, filmmaker Karim Chrobog looks at the staggering amount of food wasted in the U.S. – a problem with major human and environmental costs. The video focuses on Washington, D.C., which has taken steps to see that food ends up with those who need it rather than in landfills.READ MORE

and some might turn to eating other bird species to survive.

The EU is currently moving ahead with its ban in three phases. Now in its second year, it’s too soon to say how it is affecting seabirds. Daniel Oro, a fisheries ecologist at the Mediterranean Institute for Advanced Studies on Majorca, worries about the potential effect on the critically endangered Balearic shearwater, a seabird that frequently depends on fishery discards while rearing its young. “We are going to have smaller populations of Balearic shearwaters, that’s very clear,” said Oro. “Populations suffer a period of readapting to the new system. Many individuals are going to die, as happened with bears at Yellowstone.”

But Oro also considers the cleanup essential. Before the closing of the only dump on Majorca, he said, researchers found that many of the birds there “were low-quality individuals. They had physical problems, they had lung problems, and other diseases that were not easily seen from the outside.” The dump supported birds that natural selection would have weeded out in the wild.

Cleaning up our food waste mess and shifting wildlife populations back to natural resources increases competition and ultimately “benefits higher quality individuals,” said Oro, “so that’s good news.” But, as at Yellowstone, he acknowledged, getting there will be painful.

COMMENTS

California Safe Soil (www.calsafesoil.com) has a great new technology to recycle food supermarkets can no longer sell or donate into a liquid fertilizer called Harvest to Harvest (H2H). We use heat, mechanical action and enzymes to convert proteins, fats and carbohydrates into amino acids, organic acids and simple sugars that can be delivered through farm irrigation lines directly into the root zone to stimulate life in diverse soil organisms. Increasing soil organic matter improves soil health and increases crop yields.

There are scientifically sustainable solutions to the food waste problem - they just need to be implemented.
Dan Morash (Y'78)
Founder

Posted by
Dan Morash
on 06 Jan 2016

Thanks Richard for this interesting blog.

Our research group works at Año Nuevo Island, CA, the breeding colony of the Western Gulls that may be eating steelhead in the Osterback study. The assertion that "the number of gulls have doubled or quadrupled in different parts of the bay just since the 1980s" is based on a citation of our data (Carle et al. 2014) in the Osterback paper.

I would like to clarify that, although it is true that the population of Western Gulls has indeed risen greatly since the 1970's and 1980's at Año Nuevo, it is misleading to assume that all of this growth was fueled by human food subsidy, or even that the current population is necessarily greater than historical populations (i.e. 1800s or earlier). The Western Gull population at Año Nuevo grew from around 100-200 nests in the 70's and peaked at around 1200 nests in 2005- a lot of growth. But the 1970's numbers were at probably the lowest ebb of population, after around 100 years of disturbance and direct persecution during the mid 1800's- mid 1900's when a manned lightkeeper's station operated on Año Nuevo Island. There are no data from Año Nuevo pre-1970's, but at the Farallon Islands its well documented that the gull population was drastically reduced during the 1800's and early 1900's and only recovered when the islands were protected. Año Nuevo was protected in the 1960's and the gull population has recovered since. This may have more to do with the growth we've seen than the trash. During the 1980's-1990's increase in gull population at Año Nuevo and other nearshore colonies, there was a major decrease at the offshore Farallones, so the overall popualation in central California may have remained stable.

What's more, the Western Gull population has been annually declining at Año Nuevo since its peak in 2005. There were only 643 nests in 2015 compared with 1234 nests in 2005. Many factors could be contributing to this decline, most probably lowered availability of natural prey such as krill and forage fishes. Similar declines are being seen at the Farallones, indicating a larger scale pattern than just local landfill management.

Finally, there are several published studies showing that Western Gull reproduction is actually worse, not better, for individuals that eat a lot of trash (see multiple papers from Alcatraz Island by Pierrotti and Annett). This implies that contrary to intuition, trash may actually not help subsidize population growth in this species after all. Trash may buffer adult survival in years of poor natural food availability but this has not been thoroughly studied.

Also, the assertion that Brandt's Cormorants have declined due to reduced steelhead numbers is not entirely accurate. Though these cormorants do eat salmon sometimes, they are more influenced by species like anchovy and juvenile rockfishes. Brandt's Cormorant population trajectory is somewhat similar to the gulls'--they increased from 2 nests in 1992 to over 2,000 nests in the mid-2000's: a thousand-fold increase! Similar to the gulls, their populations dropped at the Farallones as the nearshore populations grew.

We certainly support better landfill management, which would have positive ecosystem-wide impacts. We regularly see Western Gulls dying from botulism and poisons picked up from human sources. However, the narrative that the Western Gull population has unnaturally exploded, causing them to be an unnaturally large threat to the steelhead, is more nuanced than presented here.

POST A COMMENT

Comments are moderated and will be reviewed before they are posted to ensure they are on topic, relevant, and not abusive. They may be edited for length and clarity. By filling out this form, you give Yale Environment 360 permission to publish this comment.

The Moth Snowstorm: Finding True Value in Nature’s Riches Journalist Michael McCarthy has chronicled the loss of wildlife in his native Britain and globally. In an interview with Yale Environment 360, he talks about why he believes a new defense of the natural world is needed – one based on the joy and spiritual connection it provides for humans. READ MORE

MORE IN Reports

How Tracking Product Sources May Help Save World’s Forestsby fred pearceGlobal businesses are increasingly pledging to obtain key commodities only from sources that do not contribute to deforestation. Now, nonprofit groups are deploying data tools that help hold these companies to their promises by tracing the origins of everything from soy to timber to beef.READ MORE

Full Speed Ahead: Shipping Plans Grow as Arctic Ice Fadesby ed struzikRussia, China, and other nations are stepping up preparations for the day when large numbers of cargo ships will be traversing a once-icebound Arctic Ocean. But with vessels already plying these waters, experts say the time is now to prepare for the inevitable environmental fallout.READ MORE

How Forensics Are Boosting Battle Against Wildlife Tradeby heather millarFrom rapid genetic analysis to spectrography, high-tech tools are being used to track down and prosecute perpetrators of the illegal wildlife trade. The new advances in forensics offer promise in stopping the trafficking in endangered species. READ MORE

African Wetlands Project: A Win For the Climate and the People?by winifred birdIn Senegal and other developing countries, multinational companies are investing in programs to restore mangrove forests and other wetlands that sequester carbon. But critics say these initiatives should not focus on global climate goals at the expense of the local people’s livelihoods.READ MORE

Ghost Forests: How Rising Seas Are Killing Southern Woodlandsby roger real drouinA steady increase in sea levels is pushing saltwater into U.S. wetlands, killing trees from Florida as far north as New Jersey. But with sea level projected to rise by as much as six feet this century, the destruction of coastal forests is expected to become a worsening problem worldwide.READ MORE

The Rising Environmental Toll Of China’s Offshore Island Grabby mike ivesTo stake its claim in the strategic South China Sea, China is building airstrips, ports, and other facilities on disputed islands and reefs. Scientists say the activities are destroying key coral reef ecosystems and will heighten the risks of a fisheries collapse in the region.READ MORE